Electric fuse



Patented ct, 1d, i924.

Umran stares asians PATENT onirica.

man L. cena, or cnioaec, ILLINors, Assienon To FEDERAL matarme comma', or cHIcaGo, ILLINOIS; A coarona'rron or ILLINOIS.

morale rusa.

Application lcd October 31, 1921. Serin! No. 511,882.

To: all whom t may concern: g

Be it known that I, ELMER L. OGLE, a citizen of the United States, and a resident of Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Electric Fuses; and I heren by declare that the following is a full, clear, and exact description thereof, reference being had tothe accompanying drawings and to the letters of reference marked thereon, which form a part of this specification.

This invention relates to overload circuit breakers, commonly known as fuses, adapted for use in multiphase circuits, and consists of the matters hereinafter described and more particularly pointed out in the appended claims.

The ob'ect of the invention is to improve and simplify the construction of a fuse of the kind; to reduce the cost of manufacture by making the parts easy to assemble, and

in particular to standardize and improve the construction and arrangement of the heating coil, so that it may be produced as a unit, complete and ready for insertion when assembling the parts of the cartridge.

Other novel features will be pointed out as I proceed with my specification.

In the drawings Figure 1 represents a longitudinal, central section through the improved fuse;

Figure 2 is another longitudinal, central section in a plane at ri ht angles to that of l the previous section, as indicated by the line 2 2 of Figure 1;

` Fi re 3 is a cross-section through the fuse 1n a plane indicated by the line 3-3 of Fi ure 1;

igure 4 is a perspective View of the novel heating coil unit as it a pears when ready for insertion in the cartri e;

Figures 5 and 6 are etail perspective views of parts to be more particularly described later.

Figure 7 is a perspective View of a stud used 1n the construction.

Referring now to that embodiment of the invention illustrated in the drawings The fuse comprises a body 10 of insulation material, as i'ibre or the like, with metallic heads l1, 12, each carrying a blade contact 11, 12 and an enclosed cartridge 13 containin fusible bars 14 (two as shown) and a heating coil unit 15 with terminals 16, 16

connected to spring contacts 17, 17 on the outside of the cartridge body. The construction in these respects, save for the heating coil unit itself, is substantially as disclosed in an ap lication filed by me on August 29, 1921, erial Number 496,207, and as the details 'of said construction form no part of the present invention, they need not be more particularly described here.

The heating coil unit 17 consists of a narrow elongated core 18, comprising two outer sheets 19, 19 of asbestos or like fireproof material, and an intermediate sheet 20 of mica; of a coil of resistance wire 21 of the required length, wound upon said core 18; and

of two sheets 22, 22 of mica of substantially the same length as, but wider than the core, so that they project beyond each side of the core and be ond the coil wound thereon, the several slieets being securely attached together by means of metal rivets, which extend through the five thicknesses of material at or near the ends of the unit, as clearly shown in Figure 4. The ends of the resistance wire are extended beyond the edges of the mica sheets 22, to provide the terminals 16, 16, which extend through the cartridge wall and are connected to the s ring contacts 17, as shown and as described 1n my application hereinbefore referred to.

In assembling the cartridge, the heatin coil unit 15 is inserted into the cartridge and placed in a position adjacent to and parallel to the fusible bar or bars 14, and preferably between said bars as shown, when two such bars are used. A tube of asbestos 25 is inserted within the cartridge body in advance of the insertion of the heating unit and the heating unit, which is made some* what narrower than the inner diameter of the cartridge body, is held in place by rea* son of the engagement of its lateral edges against the somewhat yielding inner surface of the asbestos tube. The powder in 'the cartridge also packs against the outer faces of the heating unit, and acts to lock it in its proper position within the tube. 'Ihe advantage and readiness of assembly of va cartridge in which is used the improved heating unit, will be manifest to those familiar with the art.

The use of the core 18 with the resistance wire 21 coiled about it, makes it possible to bring a greater length of resistance wire within the comparatively small limits of the unit. The outer mica plates or sheets 22, extendin as they do, beyond'the sides of the core, ully insulate the coil electrically and in addition act, when the coil is heated by current passing through it, to confine and. direct the heat waves into the space between the projecting edges of said plates, so that the heat is concentrated at the lateral edges of the unit to act with more effect than if scattered and diffused in all directions from the coil.

The improved fuse is provided with the following novel devices for connecting to the fuse body the wires by means of which its heatin coil 21 is connected to another circuit. See Figures 3, 5 and 7.) 23 indicates a pin or stud provided with a radial flange 24 intermediate its ends. The bottom end part 25 is threaded below the ange and the body 10 of the fuse is tapped to receive said part 25 which 'projects inwardly beyond the wall of the fuse body in position to engage one of the spring contacts 17 on `the cartridge 13. A thimble 26 made of insulation material (shown inperspective in Figure 5) is engaged upon the stud 23 and between its flange 24 and the fuse body 10. Said thimble has an apertured bottom wall 27, Hat on the inside for engagement with said stud iange and curved on the outside as indicated at 28 to fit the surface of the fuse body. Thus when the stud is inserted through the aperture in the bottom wall 27 of the thimble and screwed home into the fuse body, the thimble is securely fixed to the fuse body. The upright side walls 29, 29 of the thimble are divided by diametrically opposite slots 30, 30.

The end part3l of the stud above the flange 24 is somewhat reduced in diameter and is threaded t0 receive a thumb-nut or cap 32 consisting of a tubular, inverted cup 33, constituting a head, of hard rubber or other suitable insulating material and of an internally threaded metal sleeve 34, fixed within said cup. The thumbenut is made of a diameter to fit easily within the upright side walls 29 of the thimble. 35 indicates a washer which is engaged on the stud 23, next above its fiange 24. An end 36 of the wire leading to another circuit is looped about the stud 23, in the space between the flange 24 and the washer 35, whereupon the thumbnut is screwed down to securely grip the said loop between the washer and the flange. The thimble 26 extends considerably above the base of the thumb-nut, when the thumbnut is screwed home, as clearly shown in Figure l. Two devices of the kind are provided on each fuse body, as shown in Figure 1.

Each insulation thimble 26, by means of its upright walls 29, presents a barrier or shield to prevent arcing in the gap between the terminal connection of the wire 36 and the proximate metallic head of the fuse. It also prevents the possibility of a short circuit between said terminal connection and head by means of a tool, as a screw driver, when carelessly dropped in position to bridge said gap.

In order to adapt the fuse for use without the necessity of providing extra terminals in the line circuit in which the fuse is placed for the wires leading to the heating coil of a fuse in another circuit, the fuse heads 1l, 12, are preferably each rovided with a screw 37 and washer 38,-- e latter having diametrically disposed upstanding lugs 39 which embrace the sides of the screw head and retain the wire terminal end in a familiar manner. The screws are threaded through the tubular parts of the heads into the fuse body and are located in the diametric plane of the blades 11", 12, as shown in Fig. 1. This construction permits the use of a screw and a single washer instead of a screw and two washers as in my earlier application filed August 29, 1921 Serial Number 496,207'.

1. In combination with the tubular body of a fuse cartridge having a plurality of terminals in the wall thereof,a fusible element in said body comprising two longitudinally extending, spaced parallel bars, a heating element arranged between Said fusible bars and comprising a core of insulation material, a heating coil of wire wound upon said core with its ends attached to said terminals, plates of insulation material between which said core is engaged and held, said plates projecting atl both sides beyond said core to engage the interior part of said tubular body so as to be held in position thereby, and means for attaching said plates and core together at points beyond the end loops of the heating coil.

2. ln combination with the tubular body of a fuse cartridge having a plurality of terminals in the wall thereof, an asbestos tube fitting the interior of said body, a fusible element in said body comprising two longitudinally extending, spaced parallel bars, a heating element arranged between said fusible bars, and comprising a fiat core of mica with an asbestos sheet on each side thereof, a heating coil of wire wound upon said core with its ends attached to said terminals, plates of mica one on each side of said core, said plates projecting at both edges beyond said core and engaging said sheet of mica, a coil wound on said core, In testimony that I claim the foregoing as mica plates of substantially the length of, my invention, I aix my signature, this 13 but wider than said core, embracing said core day of October, A. D. 1921.

between them, with their lateral edges pro- ELMER L. OGLE. jecting at each Side beyond said core, and Witnesses: rivets for attachin said several plates and H. W.

sheets together at eir ends. R. L. Dm 

